Low melting point, high thermal stable branched benzoxazines resin derived from mixed-substituted phosphazene core

Abstract

Six fluorine-containing, mix-substituted phosphazene-based branched benzoxazine monomers with a low melting point were successfully prepared and their chemical structures were verified by 1 H, 13 C, 31 P and 19 F nuclear magnetic resonance (NMR). These branched benzoxazine resins underwent thermal ring-opening polymerization to form cured polymers with high thermal stability both in N 2 atmosphere and in air. The co-substituents, both m-CF 3 PhOH and p-CF 3 PhOH, imposed significant effects on processing, thermal, and surface properties of corresponding polybenzoxazines. Non-isothermal differential scanning calorimetry (DSC) under diverse heating rates was adopted to investigate the curing kinetics and determine the activation energy of polymerization. DSC results indicate that the m-CF 3 PhO-/p-CF 3 PhO-groups have the potential to lower ring-opening polymerization temperature. Glass transition temperatures (T g s) of polybenzoxazines derived from p-CF 3 PhOH are higher than that of polymers derived from m-CF 3 PhOH due to different steric hindrance and crosslinking density. More interesting, all polybenzoxazines show relatively high dielectric constant but exhibit low dielectric loss at ambient temperature.

Annealing of acetylene containing cyclotriphosphazene to generate nitrogen- and phosphorus-containing layered graphitic materials

“…1b). This and previous studies strongly suggest the exothermic processes are caused by two chemical reactions, the ring opening polymerization of the cyclotriphosphazene core (Scheme S2, ESI†) 38–40 and the crosslinking reactions of the terminal acetylene moieties. 13–15…”

“…1b). This and previous studies strongly suggest the exothermic processes are caused by two chemical reactions, the ring opening polymerization of the cyclotriphosphazene core (Scheme S2, ESI †) [38][39][40] and the crosslinking reactions of the terminal acetylene moieties. [13][14][15] To further evaluate the impact of thermal annealing on the structure and chemical nature of HPTP-Pg, thermal transitions were studied in detail by differential scanning calorimetry (DSC) and variable temperature X-ray diffraction (vt-XRD).…”

“…Heating HPTP-Pg to a much higher 350 1C in the DSC revealed an irreversible large and broad exothermic peak from about 238 1C to 300 1C. This peak is likely generated by a simultaneous ring opening polymerization of the cyclotriphosphazene core that is reported to occur between 220-250 1C, [38][39][40] and the crosslinking of the terminal acetylene groups (Scheme 1). A thermal crosslinking of terminal acetylene groups at these temperatures was previously reported by Economy et al 15 and Ochiai et al 19 The two processes clearly overlap in the DSC experiment, but it is difficult to find their individual onset temperatures because the compound quickly becomes insoluble and the mechanisms of the cross-linking reactions are not well understood.…”